Tracked vehicles such as armored personnel carrier vehicles (APC) and light/medium armor track vehicles have long been used in military exercise maneuvering and even warfare scenarios. Various aspects of development of these vehicles have been attempted so as to improve their efficiency.
Development of track shoes for these types of vehicles has also been attempted so as to improve mobility of the vehicle, reduce maintenance costs, etc.
The track shoe consists of small parts, for example a shoe body, rubber pad, end connector, etc. According to an inventor's study, the service life of each of these parts is different. They are categorized into short-term, middle-term and long-term service life. Parts with short-term service life are generally rubber parts such as the rubber pad. Parts with medium-term and long-term service life are metal parts such as the connector and metal shoe body. In the short-term category, the life cycle of the parts is extremely short. In order to realize that the short-term life cycle of the rubber pad compares with the long-term category, the life cycle of the metal shoe is not cost effective for production; rather it has to be replaced on the metal shoe body even if it is still in good condition because the rubber bushing is worn out.
Generally, conventional track shoes are divided into two types. The first type is a whole-metal shoe body type which is widely used in the United States, Russian, European countries as shown in U.S. Pat. No. 2,332,976 (Saurer et al.), U.S. Pat. No. 3,357,750 (Reynold et al.), U.S. Pat. No. 2,353,124 (Burgress) and U.S. Pat. No. 4,262,972 (Falk). Their advantages are a replaceable rubber pad and long service life of the metal shoe body. The replaceable rubber pad provides long service life by replacing the rubber pad whenever the rubber wears out. However, there are many disadvantages such as high weight, shortened short-term service life of the rubber pad, less stability and more vibration during vehicle motion. Moreover, the whole-metal shoe body requires a grouser to hold the rubber pad. The grouser limits the life-span of the rubber pad because the height of the grouser is about half the thickness of the rubber pad so the rubber pad can be used at only half of its capacity. Further, its service life reduces to 50% according to the capacity of rubber. The rubber pad is consumed whenever it hits the grouser and is thus worn out. Moreover, the grouser always damages the road when the vehicle operates in an urban environment. In addition, the elongation of rubber is also limited by the grouser. One of the problems often encountered with the grouser is that, when the track laying vehicle operates at high speed and turns abruptly, the grouser will cut the rubber pad like a knife because of vehicle speed, load and grouser's position.
The second type is rubber-block type track shoe as shown in U.S. Pat. No. 4,765,694, U.S. Pat. No. 4,765,695, U.S. Pat. No. 4,840,438, U.S. Pat. No. 4,871,216, U.S. Pat. No. 5,069,510 of General Dynamics and U.S. Pat. No. 2,375,170 of Wingfoot Corporation. The advantages are light weight, longer short-term service life of the rubber pad, more stability and less vibration during vehicle motion owing to absorption of vibration in the rubber block, as well as being economical in terms of production and fuel used. Moreover, rubber can be extended up to its full elongation and can be used up to its maximum capacity of life-span until it is thinned to a minimum thickness of rubber at the shoe body without limitation to the grouser. However, its disadvantage is shortened service life of long-term service parts because complete rubber block set has to be replaced. Even if one tried to replace only the rubber pad, this would be impossible due to the structure of metal parts.
Several well-known track shoes for tracked vehicles such as those used in conventional armored personnel carrier vehicles and light/medium combat tanks are made of a metal shoe body with a single pin and combined with a rubber pad. The rubber pad is directional and replaceable. The disadvantage of this type of track shoe is that the directional rubber pad will produce an indication in the trace making it easy to determine the direction in which the vehicle is heading, which is undesirable under warfare scenarios. In addition, with this type of track shoe, an octagonal metal rod connector is used for connecting the track shoes so as to form flexible, i.e., pivotally consecutively interconnected, track shoes. Due to the small area allowance of the bushing, one often encounters the serious problems with this type of assembly that the connector is prone to disengaging from its position or sliding off, and will then scratch against the vehicle body and damage it. Further, this type of track shoe is not suitable for maneuvering the vehicle on snow-covered terrain. If a vehicle is to be adapted to such conditions, the rubber pad must be removed which is very inconvenient. Moreover, the bare-metal track shoe only yields greater ground pressure, which causes higher friction damages to the ground or road surface, which is particularly annoying when the vehicle is operated within a town.
From the past, the army has been developing its efficiency to destroy an enemy or other target and improving its ability to go through armor. On the other hand, the armor has been improved to protect against ammunition (fire attack) accordingly. In fact, improving the defensive armor will generally increase the weight of armored plate on the vehicle. Therefore, all armored track laying vehicles have been upgraded from time to time to carry high defensive armor, for example by increasing the engine power, improving the transmission and suspension to heavy duty requirements. All those upgrades and armor have been increasing the weight of the vehicle. However, nobody has succeeded in improving the track shoe and rubber pad for higher weight vehicles. As a consequence of the high load upon each rubber pad, one of the serious problems often encountered in high temperature terrains, such as in the Middle East, is heat build up phenomena in the rubber pad; the internal rubber may even become explosive when the vehicle runs at high speed and turns abruptly.
The U.S. Pat. No. 5,069,510 (Cory) describes a track for a track laying vehicle including a track shoe, a replaceable road pad, a pin assembly for connecting pairs of the track shoes with hollow pins, and an end connector for connecting ends of the pins cooperating with a center connector in connecting the shoe assemblies.
Another, similar, known type of track shoe has been used with light tanks such as the Scorpion tank of England. However, the major disadvantage of this type of track shoe is that the rubber pad is not replaceable. Once the rubber pad becomes worn or damaged, the entire track shoe needs to be replaced, resulting in higher maintenance costs.
Therefore, there is the need for an improved track shoe assembly for tracked vehicles that enhances the mobility of the vehicle, increases the efficiency of the vehicle and makes it suitable for operation or maneuvering under various terrain types, offers high stability and vibrant absorption, provides longer service range and lifespan, is easy and economical to maintain, and is cost effective between production and utilization. The ultimate goal is to increase the capability of the vehicle when it is operating in practice or warfare scenarios with cost effectiveness and reliability of maintenance.